Thomas Abbey C, McLean Scott G, Palmieri-Smith Riann M
School of Kinesiology, University of Michigan, Ann Arbor, MI, USA.
J Appl Biomech. 2010 May;26(2):159-70. doi: 10.1123/jab.26.2.159.
Neuromuscular fatigue exacerbates abnormal landing strategies, which may increase noncontact anterior cruciate ligament (ACL) injury risk. The synergistic actions of quadriceps and hamstrings (QH) muscles are central to an upright landing posture, though the precise effect of simultaneous fatigue of these muscles on landing and ACL injury risk is unclear. Elucidating neuromechanical responses to QH fatigue thus appears important in developing more targeted fatigue-resistance intervention strategies. The current study thus aimed to examine the effects of QH fatigue on lower extremity neuromechanics during dynamic activity. Twenty-five healthy male and female volunteers performed three single-leg forward hops onto a force platform before and after QH fatigue. Fatigue was induced through sets of alternating QH concentric contractions, on an isokinetic dynamometer, until the first five repetitions of a set were performed at least 50% below QH peak torque. Three-dimensional hip and knee kinematics and normalized (body mass x height) kinetic variables were quantified for pre- and postfatigue landings and subsequently analyzed by way of repeated- measures mixed-model ANOVAs. QH fatigue produced significant increases in initial contact (IC) hip internal rotation and knee extension and external rotation angles (p < .05), with the increases in knee extension and external rotation being maintained at the time of peak vertical ground reaction force (vGRF) (p < .05). Larger knee extension and smaller knee flexion and external rotation moments were also evident at peak vGRF following fatigue (p < .05). Females landed with greater hip flexion and less abduction than males at both IC and peak vGRF as well as greater knee flexion at peak vGRF (p < .05). The peak vGRF was larger for females than males (p < .05). No sex x fatigue effects were found (p > .05). Fatigue of the QH muscles altered hip and knee neuromechanics, which may increase the risk of ACL injury. Prevention programs should incorporate methods aimed at countering QH fatigue.
神经肌肉疲劳会加剧异常的落地策略，这可能会增加非接触性前交叉韧带（ACL）损伤的风险。股四头肌和腘绳肌（QH）的协同作用对于直立的落地姿势至关重要，尽管这些肌肉同时疲劳对落地和ACL损伤风险的确切影响尚不清楚。因此，阐明对QH疲劳的神经力学反应在制定更有针对性的抗疲劳干预策略方面显得很重要。因此，本研究旨在探讨QH疲劳对动态活动期间下肢神经力学的影响。25名健康的男性和女性志愿者在QH疲劳前后在测力平台上进行了三次单腿向前跳跃。通过在等速测力计上进行一组组交替的QH向心收缩来诱导疲劳，直到一组中的前五次重复动作至少比QH峰值扭矩低50%。对疲劳前后的落地进行三维髋部和膝部运动学以及归一化（体重×身高）动力学变量的量化，并随后通过重复测量混合模型方差分析进行分析。QH疲劳导致初始接触（IC）时髋部内旋以及膝关节伸展和外旋角度显著增加（p < 0.05），膝关节伸展和外旋的增加在垂直地面反作用力（vGRF）峰值时仍保持（p < 0.05）。疲劳后在vGRF峰值时也明显出现更大的膝关节伸展以及更小的膝关节屈曲和外旋力矩（p < 0.05）。在IC和vGRF峰值时，女性落地时的髋部屈曲角度比男性更大，外展角度比男性更小，并且在vGRF峰值时膝关节屈曲角度更大（p < 0.05）。女性的vGRF峰值比男性更大（p < 0.05）。未发现性别×疲劳效应（p > 0.05）。QH肌肉的疲劳改变了髋部和膝部的神经力学，这可能会增加ACL损伤的风险。预防计划应纳入旨在对抗QH疲劳的方法。
